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Published January 22, 2016 | Published + Submitted
Journal Article Open

Improved Constraints on Cosmology and Foregrounds from BICEP2 and Keck Array Cosmic Microwave Background Data with Inclusion of 95 GHz Band


We present results from an analysis of all data taken by the BICEP2 and Keck Array cosmic microwave background (CMB) polarization experiments up to and including the 2014 observing season. This includes the first Keck Array observations at 95 GHz. The maps reach a depth of 50 nK deg in Stokes Q and U in the 150 GHz band and 127 nK deg in the 95 GHz band. We take auto- and cross-spectra between these maps and publicly available maps from WMAP and Planck at frequencies from 23 to 353 GHz. An excess over lensed ΛCDM is detected at modest significance in the 95×150 BB spectrum, and is consistent with the dust contribution expected from our previous work. No significant evidence for synchrotron emission is found in spectra such as 23×95, or for correlation between the dust and synchrotron sky patterns in spectra such as 23×353. We take the likelihood of all the spectra for a multicomponent model including lensed ΛCDM, dust, synchrotron, and a possible contribution from inflationary gravitational waves (as parametrized by the tensor-to-scalar ratio r ) using priors on the frequency spectral behaviors of dust and synchrotron emission from previous analyses of WMAP and Planck data in other regions of the sky. This analysis yields an upper limit r_(0.05) <0.09 at 95% confidence, which is robust to variations explored in analysis and priors. Combining these B-mode results with the (more model-dependent) constraints from Planck analysis of CMB temperature plus baryon acoustic oscillations and other data yields a combined limit r_(0.05) <0.07 at 95% confidence. These are the strongest constraints to date on inflationary gravitational waves.

Additional Information

© 2016 American Physical Society. Received 2 November 2015; published 20 January 2016. The Keck Array project has been made possible through support from the National Science Foundation under Grants No. ANT-1145172 (Harvard), No. ANT-1145143 (Minnesota), and No. ANT-1145248 (Stanford), and from the Keck Foundation (Caltech). The development of antenna-coupled detector technology was supported by the JPL Research and Technology Development Fund and Grants No. 06-ARPA206-0040 and No. 10-SAT10-0017 from the NASA APRA and SAT programs. The development and testing of focal planes were supported by the Gordon and Betty Moore Foundation at Caltech. Read-out electronics were supported by a Canada Foundation for Innovation grant to UBC. The computations in this Letter were run on the Odyssey cluster supported by the FAS Science Division Research Computing Group at Harvard University. The analysis effort at Stanford and SLAC is partially supported by the U.S. DOE Office of Science. We thank the staff of the U.S. Antarctic Program and, in particular, the South Pole Station without whose help this research would not have been possible. Most special thanks go to Robert Schwarz and Steffen Richter. We thank all those who have contributed past efforts to the BICEP-Keck Array series of experiments, including the BICEP1 team. We also thank the Planck and WMAP teams for the use of their data.

Attached Files

Published - PhysRevLett.116.031302.pdf

Submitted - 1510.09217v1.pdf


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